Inherited defects in signaling pathways downstream of the insulin receptor have long been suggested to contribute to human Type 2 diabetes mellitus. Here we describe a mutation in the gene encoding the protein kinase AKT2/PKBβ in a family that shows autosomal dominant inheritance of severe insulin resistance and diabetes mellitus. Expression of the mutant kinase in cultured cells disrupted insulin signaling to metabolic end-points and inhibited the function of coexpressed, wild type AKT. These findings demonstrate the central importance of AKT signaling to insulin sensitivity in humans.Most forms of diabetes are likely to be polygenic in origin, although a number of monogenic forms are being recognised (1, 2). Although rare, these monogenic examples offer insights into the function of the affected gene in humans as well as offering important clues to understanding more common forms.We have been screening genomic DNA from 104 unrelated subjects with severe insulin resistance for mutations in genes that are implicated in insulin signalling. We identified a † To whom correspondence should be addressed. E-mail: sorahill@hgmp.mrc.ac.uk. * These authors contributed equally to this work. Europe PMC Funders Group Europe PMC Funders Author ManuscriptsEurope PMC Funders Author Manuscripts missense mutation in the serine/threonine kinase gene AKT2 in one Caucasian proband.AKT2 (also known as PKBβ) is highly expressed in insulin sensitive tissues and is activated in response to growth factors and related stimuli (3, 4) a process that requires its phosphorylation by the phosphoinositide-3 phosphate-dependent kinase activities designated PDK1 and PDK2 (3). The proband, (iii)/1 (Fig. 1D), is a non-obese 34 year old female who developed diabetes mellitus at 30 years of age. The proband, her non-obese mother, (ii)/2, maternal grandmother, (i)/2, and a maternal uncle, (ii)/3, were all heterozygous for a G to A substitution predicted to result in an R to H substitution at amino acid 274 (Fig. 1 A, B). All were markedly hyperinsulinemic (Table S1) and the mother and maternal grandmother developed diabetes mellitus in their late 30′s. Three other first-degree relatives available for study were all clinically normal with normal fasting glucose and insulin and were homozygous for the wild-type AKT2 sequence ( Fig. 1D and Table S1). This mutation was not found in genomic DNA of 1500 Caucasian control subjects from the UK.R274 forms part of an RD sequence motif within the catalytic loop of the AKT2 kinase domain that is invariant in AKT isoforms in all species, and is also highly conserved within the protein kinase family (Fig. 1C) (5). The RD motif includes the invariant D residue (D275 of AKT2) that performs an essential catalytic function in all protein kinases.R274 is positioned in the core of the catalytic domain, forming critical hydrogen bonds with the phosphate moiety of phosphoT309 in the activation segment permitting correct positioning the substrate peptide relative to the catalytic base and adenosine triphosphate (A...

No abstract

To use proteomic analysis of cerebrospinal fluid to discover novel proteins and peptides able to differentiate between patients with stable mild cognitive impairment (MCI) and those who will progress to Alzheimer disease (AD). Design: Baseline cerebrospinal fluid samples from patients with MCI and healthy controls were profiled using surface-enhanced laser desorption/ionization time-offlight mass spectrometry. Setting: Memory disorder clinic. Participants: Patients with MCI (n = 113), of whom 56 were cognitively stable and 57 progressed to AD with dementia during a 4-to 6-year follow-up, as well as 28 healthy controls who were followed up for 3 years. Main Outcome Measure: During follow-up, 57 patients progressed to AD and 56 patients had stable MCI. Cerebrospinal fluid from these 2 groups of patients was compared using surface-enhanced laser desorption/ ionization time-of-flight mass spectrometry. Results: We identified a panel of 17 potential biomarkers that could distinguish between patients with stable MCI and patients with MCI who progressed to AD. We have positively identified and characterized 5 of the potential biomarkers. Conclusions: Proteomic profiling of cerebrospinal fluid provided a novel panel of 17 potential biomarkers for prediction of MCI progression to AD. The 5 identified biomarkers are relevant to the pathogenesis of AD and could help gain an understanding of the molecular pathways in which they may function.

No abstract